In recent years, attention has been paid to utilization of biomass as energy. Known methods for utilizing biomass as energy include a method which directly burns biomass to obtain thermal and electrical energy, a method which obtains a fuel gas by pyrolysis, and so on.
FIG. 7 is a schematic configurational drawing of a power generation system equipped with a fuel gas purification apparatus for purifying a fuel gas from biomass according to a conventional technology.
As shown there, a carbonizer 1 heats supplied biomass to yield a pyrolysis gas and a carbonization product, and supplies them to the interior of a furnace 2. The furnace 2 is composed of a gasification and combustion section as a lower section, and a gas reforming section as an upper section. In the lower gasification and combustion section, the carbonization product supplied from the carbonizer 1 is partly burned by air or oxygen separately supplied to produce a high temperature gas, and the high temperature gas is guided to the upper gas reforming section. In the upper gas reforming section, the pyrolysis gas supplied from the carbonizer 1 is reformed in a high temperature zone attributed to the high temperature gas, whereby a crude gas containing ash and impurities is produced. The crude gas is desulfurized and dedusted by a gas purification device 10 to purify a fuel gas consisting essentially of carbon monoxide and hydrogen.
The so produced fuel gas is supplied to a power generation means 20 composed, for example, of a gas turbine, a fuel cell or the like, and the power generation means 20 generates electric power with the use of this fuel gas. The fuel gas is also used otherwise as a material for a synthetic liquid fuel.
Waste heat generated by the power generation means 20 is sent to the carbonizer 1 to be utilized as a heat source for heating the biomass.
The conventional gas purification device 10 is composed of a dedusting device, a COS converter, a desulfurizer, a gas cooler, a gas cleaner, etc. in order to remove ash, tar and impurities in the crude gas. Thus, the equipment configuration for performing gas purification has become complicated, thereby making it difficult to enhance the operability of the equipment, and resulting in a cost increase.
Furthermore, air and nitrogen are supplied from the outside into the furnace 2 in order to burn the carbonization product in the gasification and combustion section of the furnace 2. Thus, the fuel gas (crude gas) is diluted with the air, nitrogen, etc., with the result that the calories, per unit volume, of the fuel gas are decreased.
The following patent document 1 exists as a publication which discloses the same type of technology as the above-described conventional technology.    Patent Document 1: JP-A-2006-2042